Part 2 of Metz to Nikon flash conversion
iTTL Nikon Protocol
Metz SCA 3000 interface for Metz45 – part 2
In the previous document I describe the i-TTL protocol from Nikon. In this document, I will focus on the implementation of this protocol connecting Metz 45 CL-3 or CL4 with Nikon DSLR.
Hardware interface
As mention previously the hot shoe interface will be define as 0-5V technology even if the devices use 0-3.3V level during data exchange. Before protocol activation, signal reach 4 to 5V... No safe to use 3V CPU or must accept 5V.
On Flash side, using SCA3000 M1 cable the interface will be TTL 5V (some signal have to be adapted but it is 5V interface). One analog input is needed to acquire the mode signal from the flash.
The micro CPU must be small as it must enter in the SCA shoe adapter type SCA 3401. This is the most difficult point.
Then I chose a fast micro CPU working at 5V level with efficient software tools. I select Teensy 2.0 board, Arduino software environment with Teensyduino library. The CPU speed is acceptable if well programmed. For your information the latency of Sync X signal is similar to SB-900.
The input accepts 2.5 to 3V signal. It is not the case of all Arduino board. Lose 1 day with a bad clone of Arduino V3.
SCA 3000 system from Metz
Metz Company developed flash system with universal adapter for Film camera. They start with SCA300 series adapter for non-autofocus SLR and develop SCA 3000 when autofocus SLR arrived on the market.
SCA 3000 system for 45 CL-3 or CL-4 flash is composed as follow:
Could certainly work with 45CT-3 or CT4 and 38CT3 but flash stop signal (Metz pin 9) must be checked before any test.
Software project
Software is the main component of the interface between Metz Mecablitz 45 CL-3 or CL-4 flash series and Nikon DSLR.
Software is developed using Arduino tool environment.
Software features
The software manage Nikon i-TTL data exchange with DSLR ignoring some information like zoom, ISO, aperture but managing flash power control in TTL and generating adequate frame to insure correct handshake between flash and camera.
